Conventionally, a pressurized fluidized bed incinerator system is known as incineration facilities where a material to be treated such as sewage sludge, biomass, and municipal solid wastes is burned, utilizing energy of a flue gas exhausted from an incinerator.
The pressurized fluidized bed incinerator system comprises a pressurized fluidized bed incinerator for burning the material to be treated, a turbocharger having a turbine rotated by the flue gas exhausted from the pressurized fluidized bed incinerator and a compressor rotated according to the rotation of the turbine for supplying a combustion air. Further in the pressurized fluidized bed incinerator system, a dust collector is provided between the pressurized fluidized bed incinerator and the turbocharger for collecting impurities contained in the flue gas so that damage caused by the impurities on bearing and impeller of the turbine can be prevented and air pollution control can be performed.
The pressurized fluidized bed incinerator system can be self-driven, because the total amount of the required combustion air for the combustion of the material to be treated is supplied from the turbocharger to the pressurized fluidized bed incinerator. Accordingly, it is known that a forced draft blower or an induced draft fan required in a conventional system are not necessary, resulting in reduced running costs.
Methods for conveying impurities from pressurized fluidized bed boilers or the like under pressurized state were proposed, in each of which, impurities contained in a flue gas are collected by a dust collector, and conveyed to the outside by way of a conveyer, a high pressure ash hopper, and a low pressure ash hopper provided below the dust collector (see Patent Literatures 1 to 4).
Patent Literature 1 discloses a technique in which fine combustible dusts contained in residue are dispersed by an air flow and a gas containing the fine dusts as well as a combustion air altogether are returned back to a tuyere of a melting furnace so that the fine combustible dusts are combusted, using two stages of dumpers and a pressure equalizing pipe system for equalization before and after the two stages of dumpers and between the dumpers to adjust the pressures between a dust collection system and the melting furnace having different pressures.
Patent Literature 2 and Patent Literature 3 disclose techniques each of which comprises a collector for collecting ash contained in a flue gas of a pressurized fluidized bed boiler using coal as fuel, a high pressure ash tank for receiving the ash under a maintained high pressure state of the flue gas, a separator for separating the ash from a conveyance gas in the high pressure ash tank, a pressure reducing device for releasing a gas from the high pressure ash tank, and an ash discharge valve and an airtight valve provided below the high pressure ash tank having a hopper-shaped lower portion while the ash is cooled to improve the reliability and the durability thereof.
After collecting dusts from a flue gas from a blast furnace with a high pressure, for a conventional apparatus for conveying the dusts, an intermediate hopper above a screw conveyer, a sealing valve for equally releasing the pressure at the upper side and the lower side of the intermediate hopper, and a dust separating rotary valve are required, resulting in the complicated and large apparatus. In order to solve this problem, Patent Literature 4 discloses a technique in which a disperser is provided below a dust discharge valve provided below a dust collector lower hopper, and a pipe having not only pressure equalization function but also capability of increasing the pressure is further provided between a disperser gas inlet and a dust collector outlet pipe with a pressure increasing blower interposed therebetween so that the dusts can be conveyed with the air to the dust hopper.